Answer:
The correct option is:
D) 589.3 nm
Explanation:
Energy of one photon = 

Hence, the wavelength (in nm) of radiation is 589.7nm (approximately equal to 589.3nm)
Alpha and Beta particles can be stopped by our skin. Gamma particles cannot be stopped by our skin.
I would say #3 I’m sorry if it’s wrong tho
Put the cation (a positive ion, the metal in this case,) without changing anything, then the nonmetal, or anion. For the nonmetal, change the ending to -ide. For example, if you have potassium and chlorine, you would have potassium chloride. Hope this helps!